package panda.lang.time;


import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.TimeZone;

import panda.lang.Strings;

/**
 * <p>Duration formatting utilities and constants. The following table describes the tokens 
 * used in the pattern language for formatting. </p>
 * <table border="1">
 *  <tr><th>character</th><th>duration element</th></tr>
 *  <tr><td>y</td><td>years</td></tr>
 *  <tr><td>M</td><td>months</td></tr>
 *  <tr><td>d</td><td>days</td></tr>
 *  <tr><td>H</td><td>hours</td></tr>
 *  <tr><td>m</td><td>minutes</td></tr>
 *  <tr><td>s</td><td>seconds</td></tr>
 *  <tr><td>S</td><td>milliseconds</td></tr>
 * </table>
 *
 */
public class DurationFormatUtils {
	/**
	 * <p>
	 * DurationFormatUtils instances should NOT be constructed in standard programming.
	 * </p>
	 * <p>
	 * This constructor is public to permit tools that require a JavaBean instance to operate.
	 * </p>
	 */
	public DurationFormatUtils() {
		super();
	}

	/**
	 * <p>
	 * Pattern used with <code>FastDateFormat</code> and <code>SimpleDateFormat</code> for the
	 * ISO8601 period format used in durations.
	 * </p>
	 * 
	 * @see java.text.SimpleDateFormat
	 */
	public static final String ISO_EXTENDED_FORMAT_PATTERN = "'P'yyyy'Y'M'M'd'DT'H'H'm'M's.S'S'";

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Formats the time gap as a string.
	 * </p>
	 * <p>
	 * The format used is ISO8601-like: <i>H</i>:<i>m</i>:<i>s</i>.<i>S</i>.
	 * </p>
	 * 
	 * @param durationMillis the duration to format
	 * @return the formatted duration, not null
	 */
	public static String formatDurationHMS(long durationMillis) {
		return formatDuration(durationMillis, "HH:mm:ss.SSS");
	}

	/**
	 * <p>
	 * Formats the time gap as a string.
	 * </p>
	 * <p>
	 * The format used is the ISO8601 period format.
	 * </p>
	 * <p>
	 * This method formats durations using the days and lower fields of the ISO format pattern, such
	 * as P7D6TH5M4.321S.
	 * </p>
	 * 
	 * @param durationMillis the duration to format
	 * @return the formatted duration, not null
	 */
	public static String formatDurationISO(long durationMillis) {
		return formatDuration(durationMillis, ISO_EXTENDED_FORMAT_PATTERN, false);
	}

	/**
	 * <p>
	 * Formats the time gap as a string, using the specified format, and padding with zeros and
	 * using the default timezone.
	 * </p>
	 * <p>
	 * This method formats durations using the days and lower fields of the format pattern. Months
	 * and larger are not used.
	 * </p>
	 * 
	 * @param durationMillis the duration to format
	 * @param format the way in which to format the duration, not null
	 * @return the formatted duration, not null
	 */
	public static String formatDuration(long durationMillis, String format) {
		return formatDuration(durationMillis, format, true);
	}

	/**
	 * <p>
	 * Formats the time gap as a string, using the specified format. Padding the left hand side of
	 * numbers with zeroes is optional and the timezone may be specified.
	 * </p>
	 * <p>
	 * This method formats durations using the days and lower fields of the format pattern. Months
	 * and larger are not used.
	 * </p>
	 * 
	 * @param durationMillis the duration to format
	 * @param format the way in which to format the duration, not null
	 * @param padWithZeros whether to pad the left hand side of numbers with 0's
	 * @return the formatted duration, not null
	 */
	public static String formatDuration(long durationMillis, String format, boolean padWithZeros) {

		Token[] tokens = lexx(format);

		int days = 0;
		int hours = 0;
		int minutes = 0;
		int seconds = 0;
		int milliseconds = 0;

		if (Token.containsTokenWithValue(tokens, d)) {
			days = (int)(durationMillis / DateTimes.MILLIS_PER_DAY);
			durationMillis = durationMillis - (days * DateTimes.MILLIS_PER_DAY);
		}
		if (Token.containsTokenWithValue(tokens, H)) {
			hours = (int)(durationMillis / DateTimes.MILLIS_PER_HOUR);
			durationMillis = durationMillis - (hours * DateTimes.MILLIS_PER_HOUR);
		}
		if (Token.containsTokenWithValue(tokens, m)) {
			minutes = (int)(durationMillis / DateTimes.MILLIS_PER_MINUTE);
			durationMillis = durationMillis - (minutes * DateTimes.MILLIS_PER_MINUTE);
		}
		if (Token.containsTokenWithValue(tokens, s)) {
			seconds = (int)(durationMillis / DateTimes.MILLIS_PER_SECOND);
			durationMillis = durationMillis - (seconds * DateTimes.MILLIS_PER_SECOND);
		}
		if (Token.containsTokenWithValue(tokens, S)) {
			milliseconds = (int)durationMillis;
		}

		return format(tokens, 0, 0, days, hours, minutes, seconds, milliseconds, padWithZeros);
	}

	/**
	 * <p>
	 * Formats an elapsed time into a plurialization correct string.
	 * </p>
	 * <p>
	 * This method formats durations using the days and lower fields of the format pattern. Months
	 * and larger are not used.
	 * </p>
	 * 
	 * @param durationMillis the elapsed time to report in milliseconds
	 * @param suppressLeadingZeroElements suppresses leading 0 elements
	 * @param suppressTrailingZeroElements suppresses trailing 0 elements
	 * @return the formatted text in days/hours/minutes/seconds, not null
	 */
	public static String formatDurationWords(long durationMillis,
			boolean suppressLeadingZeroElements, boolean suppressTrailingZeroElements) {

		// This method is generally replacable by the format method, but
		// there are a series of tweaks and special cases that require
		// trickery to replicate.
		String duration = formatDuration(durationMillis,
			"d' days 'H' hours 'm' minutes 's' seconds'");
		if (suppressLeadingZeroElements) {
			// this is a temporary marker on the front. Like ^ in regexp.
			duration = " " + duration;
			String tmp = Strings.replaceOnce(duration, " 0 days", "");
			if (tmp.length() != duration.length()) {
				duration = tmp;
				tmp = Strings.replaceOnce(duration, " 0 hours", "");
				if (tmp.length() != duration.length()) {
					duration = tmp;
					tmp = Strings.replaceOnce(duration, " 0 minutes", "");
					duration = tmp;
					if (tmp.length() != duration.length()) {
						duration = Strings.replaceOnce(tmp, " 0 seconds", "");
					}
				}
			}
			if (duration.length() != 0) {
				// strip the space off again
				duration = duration.substring(1);
			}
		}
		if (suppressTrailingZeroElements) {
			String tmp = Strings.replaceOnce(duration, " 0 seconds", "");
			if (tmp.length() != duration.length()) {
				duration = tmp;
				tmp = Strings.replaceOnce(duration, " 0 minutes", "");
				if (tmp.length() != duration.length()) {
					duration = tmp;
					tmp = Strings.replaceOnce(duration, " 0 hours", "");
					if (tmp.length() != duration.length()) {
						duration = Strings.replaceOnce(tmp, " 0 days", "");
					}
				}
			}
		}
		// handle plurals
		duration = " " + duration;
		duration = Strings.replaceOnce(duration, " 1 seconds", " 1 second");
		duration = Strings.replaceOnce(duration, " 1 minutes", " 1 minute");
		duration = Strings.replaceOnce(duration, " 1 hours", " 1 hour");
		duration = Strings.replaceOnce(duration, " 1 days", " 1 day");
		return duration.trim();
	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * Formats the time gap as a string.
	 * </p>
	 * <p>
	 * The format used is the ISO8601 period format.
	 * </p>
	 * 
	 * @param startMillis the start of the duration to format
	 * @param endMillis the end of the duration to format
	 * @return the formatted duration, not null
	 */
	public static String formatPeriodISO(long startMillis, long endMillis) {
		return formatPeriod(startMillis, endMillis, ISO_EXTENDED_FORMAT_PATTERN, false,
			TimeZone.getDefault());
	}

	/**
	 * <p>
	 * Formats the time gap as a string, using the specified format. Padding the left hand side of
	 * numbers with zeroes is optional.
	 * 
	 * @param startMillis the start of the duration
	 * @param endMillis the end of the duration
	 * @param format the way in which to format the duration, not null
	 * @return the formatted duration, not null
	 */
	public static String formatPeriod(long startMillis, long endMillis, String format) {
		return formatPeriod(startMillis, endMillis, format, true, TimeZone.getDefault());
	}

	/**
	 * <p>
	 * Formats the time gap as a string, using the specified format. Padding the left hand side of
	 * numbers with zeroes is optional and the timezone may be specified.
	 * </p>
	 * <p>
	 * When calculating the difference between months/days, it chooses to calculate months first. So
	 * when working out the number of months and days between January 15th and March 10th, it choose
	 * 1 month and 23 days gained by choosing January->February = 1 month and then calculating days
	 * forwards, and not the 1 month and 26 days gained by choosing March -> February = 1 month and
	 * then calculating days backwards.
	 * </p>
	 * <p>
	 * For more control, the <a href="http://joda-time.sf.net/">Joda-Time</a> library is
	 * recommended.
	 * </p>
	 * 
	 * @param startMillis the start of the duration
	 * @param endMillis the end of the duration
	 * @param format the way in which to format the duration, not null
	 * @param padWithZeros whether to pad the left hand side of numbers with 0's
	 * @param timezone the millis are defined in
	 * @return the formatted duration, not null
	 */
	public static String formatPeriod(long startMillis, long endMillis, String format,
			boolean padWithZeros, TimeZone timezone) {

		// Used to optimise for differences under 28 days and
		// called formatDuration(millis, format); however this did not work
		// over leap years.
		// TODO: Compare performance to see if anything was lost by
		// losing this optimisation.

		Token[] tokens = lexx(format);

		// timezones get funky around 0, so normalizing everything to GMT
		// stops the hours being off
		Calendar start = Calendar.getInstance(timezone);
		start.setTime(new Date(startMillis));
		Calendar end = Calendar.getInstance(timezone);
		end.setTime(new Date(endMillis));

		// initial estimates
		int milliseconds = end.get(Calendar.MILLISECOND) - start.get(Calendar.MILLISECOND);
		int seconds = end.get(Calendar.SECOND) - start.get(Calendar.SECOND);
		int minutes = end.get(Calendar.MINUTE) - start.get(Calendar.MINUTE);
		int hours = end.get(Calendar.HOUR_OF_DAY) - start.get(Calendar.HOUR_OF_DAY);
		int days = end.get(Calendar.DAY_OF_MONTH) - start.get(Calendar.DAY_OF_MONTH);
		int months = end.get(Calendar.MONTH) - start.get(Calendar.MONTH);
		int years = end.get(Calendar.YEAR) - start.get(Calendar.YEAR);

		// each initial estimate is adjusted in case it is under 0
		while (milliseconds < 0) {
			milliseconds += 1000;
			seconds -= 1;
		}
		while (seconds < 0) {
			seconds += 60;
			minutes -= 1;
		}
		while (minutes < 0) {
			minutes += 60;
			hours -= 1;
		}
		while (hours < 0) {
			hours += 24;
			days -= 1;
		}

		if (Token.containsTokenWithValue(tokens, M)) {
			while (days < 0) {
				days += start.getActualMaximum(Calendar.DAY_OF_MONTH);
				months -= 1;
				start.add(Calendar.MONTH, 1);
			}

			while (months < 0) {
				months += 12;
				years -= 1;
			}

			if (!Token.containsTokenWithValue(tokens, y) && years != 0) {
				while (years != 0) {
					months += 12 * years;
					years = 0;
				}
			}
		}
		else {
			// there are no M's in the format string

			if (!Token.containsTokenWithValue(tokens, y)) {
				int target = end.get(Calendar.YEAR);
				if (months < 0) {
					// target is end-year -1
					target -= 1;
				}

				while ((start.get(Calendar.YEAR) != target)) {
					days += start.getActualMaximum(Calendar.DAY_OF_YEAR)
							- start.get(Calendar.DAY_OF_YEAR);

					// Not sure I grok why this is needed, but the brutal tests show it is
					if (start instanceof GregorianCalendar
							&& start.get(Calendar.MONTH) == Calendar.FEBRUARY
							&& start.get(Calendar.DAY_OF_MONTH) == 29) {
						days += 1;
					}

					start.add(Calendar.YEAR, 1);

					days += start.get(Calendar.DAY_OF_YEAR);
				}

				years = 0;
			}

			while (start.get(Calendar.MONTH) != end.get(Calendar.MONTH)) {
				days += start.getActualMaximum(Calendar.DAY_OF_MONTH);
				start.add(Calendar.MONTH, 1);
			}

			months = 0;

			while (days < 0) {
				days += start.getActualMaximum(Calendar.DAY_OF_MONTH);
				months -= 1;
				start.add(Calendar.MONTH, 1);
			}

		}

		// The rest of this code adds in values that
		// aren't requested. This allows the user to ask for the
		// number of months and get the real count and not just 0->11.

		if (!Token.containsTokenWithValue(tokens, d)) {
			hours += 24 * days;
			days = 0;
		}
		if (!Token.containsTokenWithValue(tokens, H)) {
			minutes += 60 * hours;
			hours = 0;
		}
		if (!Token.containsTokenWithValue(tokens, m)) {
			seconds += 60 * minutes;
			minutes = 0;
		}
		if (!Token.containsTokenWithValue(tokens, s)) {
			milliseconds += 1000 * seconds;
			seconds = 0;
		}

		return format(tokens, years, months, days, hours, minutes, seconds, milliseconds,
			padWithZeros);
	}

	// -----------------------------------------------------------------------
	/**
	 * <p>
	 * The internal method to do the formatting.
	 * </p>
	 * 
	 * @param tokens the tokens
	 * @param years the number of years
	 * @param months the number of months
	 * @param days the number of days
	 * @param hours the number of hours
	 * @param minutes the number of minutes
	 * @param seconds the number of seconds
	 * @param milliseconds the number of millis
	 * @param padWithZeros whether to pad
	 * @return the formatted string
	 */
	static String format(Token[] tokens, int years, int months, int days, int hours, int minutes,
			int seconds, int milliseconds, boolean padWithZeros) {
		StringBuilder buffer = new StringBuilder();
		boolean lastOutputSeconds = false;
		int sz = tokens.length;
		for (int i = 0; i < sz; i++) {
			Token token = tokens[i];
			Object value = token.getValue();
			int count = token.getCount();
			if (value instanceof StringBuilder) {
				buffer.append(value.toString());
			}
			else {
				if (value == y) {
					buffer.append(padWithZeros ? Strings.leftPad(Integer.toString(years), count,
						'0') : Integer.toString(years));
					lastOutputSeconds = false;
				}
				else if (value == M) {
					buffer.append(padWithZeros ? Strings.leftPad(Integer.toString(months), count,
						'0') : Integer.toString(months));
					lastOutputSeconds = false;
				}
				else if (value == d) {
					buffer
						.append(padWithZeros ? Strings.leftPad(Integer.toString(days), count, '0') : Integer
							.toString(days));
					lastOutputSeconds = false;
				}
				else if (value == H) {
					buffer.append(padWithZeros ? Strings.leftPad(Integer.toString(hours), count,
						'0') : Integer.toString(hours));
					lastOutputSeconds = false;
				}
				else if (value == m) {
					buffer.append(padWithZeros ? Strings.leftPad(Integer.toString(minutes), count,
						'0') : Integer.toString(minutes));
					lastOutputSeconds = false;
				}
				else if (value == s) {
					buffer.append(padWithZeros ? Strings.leftPad(Integer.toString(seconds), count,
						'0') : Integer.toString(seconds));
					lastOutputSeconds = true;
				}
				else if (value == S) {
					if (lastOutputSeconds) {
						milliseconds += 1000;
						String str = padWithZeros ? Strings.leftPad(Integer.toString(milliseconds),
							count, '0') : Integer.toString(milliseconds);
						buffer.append(str.substring(1));
					}
					else {
						buffer.append(padWithZeros ? Strings.leftPad(
							Integer.toString(milliseconds), count, '0') : Integer
							.toString(milliseconds));
					}
					lastOutputSeconds = false;
				}
			}
		}
		return buffer.toString();
	}

	static final Object y = "y";
	static final Object M = "M";
	static final Object d = "d";
	static final Object H = "H";
	static final Object m = "m";
	static final Object s = "s";
	static final Object S = "S";

	/**
	 * Parses a classic date format string into Tokens
	 * 
	 * @param format the format to parse, not null
	 * @return array of Token[]
	 */
	static Token[] lexx(String format) {
		char[] array = format.toCharArray();
		ArrayList<Token> list = new ArrayList<Token>(array.length);

		boolean inLiteral = false;
		StringBuilder buffer = null;
		Token previous = null;
		int sz = array.length;
		for (int i = 0; i < sz; i++) {
			char ch = array[i];
			if (inLiteral && ch != '\'') {
				buffer.append(ch); // buffer can't be null if inLiteral is true
				continue;
			}
			Object value = null;
			switch (ch) {
			// TODO: Need to handle escaping of '
			case '\'':
				if (inLiteral) {
					buffer = null;
					inLiteral = false;
				}
				else {
					buffer = new StringBuilder();
					list.add(new Token(buffer));
					inLiteral = true;
				}
				break;
			case 'y':
				value = y;
				break;
			case 'M':
				value = M;
				break;
			case 'd':
				value = d;
				break;
			case 'H':
				value = H;
				break;
			case 'm':
				value = m;
				break;
			case 's':
				value = s;
				break;
			case 'S':
				value = S;
				break;
			default:
				if (buffer == null) {
					buffer = new StringBuilder();
					list.add(new Token(buffer));
				}
				buffer.append(ch);
			}

			if (value != null) {
				if (previous != null && previous.getValue() == value) {
					previous.increment();
				}
				else {
					Token token = new Token(value);
					list.add(token);
					previous = token;
				}
				buffer = null;
			}
		}
		return list.toArray(new Token[list.size()]);
	}

	// -----------------------------------------------------------------------
	/**
	 * Element that is parsed from the format pattern.
	 */
	static class Token {

		/**
		 * Helper method to determine if a set of tokens contain a value
		 * 
		 * @param tokens set to look in
		 * @param value to look for
		 * @return boolean <code>true</code> if contained
		 */
		static boolean containsTokenWithValue(Token[] tokens, Object value) {
			int sz = tokens.length;
			for (int i = 0; i < sz; i++) {
				if (tokens[i].getValue() == value) {
					return true;
				}
			}
			return false;
		}

		private final Object value;
		private int count;

		/**
		 * Wraps a token around a value. A value would be something like a 'Y'.
		 * 
		 * @param value to wrap
		 */
		Token(Object value) {
			this.value = value;
			this.count = 1;
		}

		/**
		 * Wraps a token around a repeated number of a value, for example it would store 'yyyy' as a
		 * value for y and a count of 4.
		 * 
		 * @param value to wrap
		 * @param count to wrap
		 */
		Token(Object value, int count) {
			this.value = value;
			this.count = count;
		}

		/**
		 * Adds another one of the value
		 */
		void increment() {
			count++;
		}

		/**
		 * Gets the current number of values represented
		 * 
		 * @return int number of values represented
		 */
		int getCount() {
			return count;
		}

		/**
		 * Gets the particular value this token represents.
		 * 
		 * @return Object value
		 */
		Object getValue() {
			return value;
		}

		/**
		 * Supports equality of this Token to another Token.
		 * 
		 * @param obj2 Object to consider equality of
		 * @return boolean <code>true</code> if equal
		 */
		@Override
		public boolean equals(Object obj2) {
			if (obj2 instanceof Token) {
				Token tok2 = (Token)obj2;
				if (this.value.getClass() != tok2.value.getClass()) {
					return false;
				}
				if (this.count != tok2.count) {
					return false;
				}
				if (this.value instanceof StringBuilder) {
					return this.value.toString().equals(tok2.value.toString());
				}
				else if (this.value instanceof Number) {
					return this.value.equals(tok2.value);
				}
				else {
					return this.value == tok2.value;
				}
			}
			return false;
		}

		/**
		 * Returns a hash code for the token equal to the hash code for the token's value. Thus 'TT'
		 * and 'TTTT' will have the same hash code.
		 * 
		 * @return The hash code for the token
		 */
		@Override
		public int hashCode() {
			return this.value.hashCode();
		}

		/**
		 * Represents this token as a String.
		 * 
		 * @return String representation of the token
		 */
		@Override
		public String toString() {
			return Strings.repeat(this.value.toString(), this.count);
		}
	}

}
